The embodiments described herein relate generally to systems and methods for arc flash detection and mitigation and, more particularly, to arc flash detection and mitigation systems that provide continuous protection and facilitate reducing false detections.
At least some known electric distribution circuits, such as switchgear units, have conductors that are separated by insulation, such as air, or gas or solid dielectrics. However, if the conductors are positioned too closely together, or if a voltage between the conductors exceeds the insulative properties of the insulation between the conductors, an arc flash can occur. For example, the insulation between the conductors can become ionized, which makes the insulation conductive and enables formation of an arc flash.
An arc flash includes a rapid release of energy due to a fault between two phase conductors, between a phase conductor and a neutral conductor, and/or between a phase conductor and a ground point. An arc flash can release significant energy in the form of heat, intense light, pressure waves, and/or sound waves, sufficient to damage the conductors and adjacent equipment. More specifically, arc flash temperatures can reach, or exceed, 20,000° C., vaporizing the conductors and adjacent equipment. To mitigate the damage caused during an arc flash, known arc flash mitigation devices generate a controlled short circuit that starves the arc flash of energy. However, known arc flash mitigation devices significantly disrupt the service of the electric distribution circuit after tripping, also referred to as engaging. For example, the electric distribution circuit may be disrupted until a technician manually inspects, repairs, and/or resets the system. Accordingly, “nuisance trips” (i.e., trips caused by falsely detecting an arc flash) impose significant costs on operators of electric distribution circuits.
In particular, some known arc flash mitigation devices are designed to engage based on measured currents that indicate an arc flash is occurring. However, the current level of a fault that generates an arc flash may be less than the current level of a short circuit, causing arc flashes to be detected during some standard short circuits. In addition, standard circuit breakers may not be able to clear the short circuit before the arc flash mitigation system engages, disrupting service by the electric distribution circuit. Accordingly, known current based arc flash mitigation devices may disrupt service after falsely detecting an arc flash that may have been recoverable using a standard circuit breaker.
Some other known arc flash mitigation systems use light sensors to detect the presence of light emitted during an arc flash. However, such sensors are often sensitive to low light levels such that they also detect non-arc-flash light and trigger a “nuisance trip” of the arc flash mitigation device. For example, a typical arc flash event can produce light with luminous flux on the order of 100,000 lux at a distance of three to four feet from the arc flash event, while known light sensors generally saturate at 700 lux or less. Light emitted by a circuit breaker during a trip, by space lighting, or by direct sunlight, may cause the light sensor to falsely detect an arc flash event.
Due to the costs associated with “nuisance trips”, many known arc flash mitigation devices are operated only during specific time periods, for example, when a technician is operating on the electric distribution circuit. Thus, there is a need for an arc flash detection system that can operate continuously, reliably detects arc flash events to mitigate nuisance trips, and operate quickly to facilitate preventing injury to technicians and equipment.